Refining process



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REFNING PROCESS Filed Feb. 18, 1941 /N/ 'r/AL y l cooA /NC ssc ONDA RY lZONE oNruss/alv l kzam: g I.

:ww 2 n 2q l 2232? .same by various processes.

Patented Feb. 24, 1942 UNITEDVSTATES PATENT OFFICE REFINING PROCESSwalter 1i. Rupp, Mountainsiae, N. J., assigner to Standard OilDevelopment Company, a corporation of Delaware Application February 18,1941, Serial No. 379,391A

4 Claims. Cl. 62--175.5)

The present invention is concerned with a process for the segregationand recovery of valuable hydrocarbon constituents from feed gas mixturescontaining the same. The invention is more particularly directed to anAimproved process comprising compressing, cooling and stripping stagesby which it is possible to eiliciently and economically recover andsegregate hydrocarbon constituents containing four or more carbon `atomsin the molecule from normally gaseous hydrocarbon feed constituentscontaining the same.

vIn accordance with the present process, feed gases containingrecoverable hydrocarbons, se-

.cured in the refining of petroleumv oils, as for example fromdistillation, reforming, cracking or related refining operations, arecompressed and the hot gases separated into primary and secondary feedgas streams. The primary feed gas stream is cooled and passed into aninitial separation zone in which the liquid condensate is separated as aprimary condensate from the uncondensed vapors. The uncondensed vaporsare withdrawn from the initial separation zone,

further compressed, cooled, and passed into a secondary separation zone.The liquid condensate from' the secondary separation zone, andpreferably at least a portion of the primary condensate, are combinedand passed to a stripping zone in which the condensates countercurrentlythe quantities of the feed gases are relatively W, v

or when the feed gases are derived in rather isolated areas where steamgeneration facilities are not available for reboiling. Inaccordance withmy process, valuable hydrocarbon constituents may be readily andelciently segregated from feed gases containing the same, utilizing anovel arrangement of compressing, cooling and strip- I ping zones.

contact the secondary stream of hot feed gases.`-

A stripped liquid hydrocarbon product substantially free of undesirablehydrocarbon constituents is withdrawn from the bottom of the strippingzone, whileuncondensed gases are withdrawn overhead from the strippingzone and combined with the primary stream of hot feed gases passed tothe initial cooling zone.

lt is well-known in the art to segregate valuableY hydrocarbonconstituents which may be utilized in motor fuels from gases containingthe For example, it is known to contact feed gases containingrecoverable hydrocarbons which may be included in motor fuels and thclike with various solid adsorbents which have a preferential selectivityfor the valuable hydrocarbon constituents. The adsorbed hydrocarbons arerecovered from the adsorbent usually by heating the same. The commonpractice, however, for the recovery of these hydrocarbon constituents-isto countercurrently contact feed gases under various temperature andpressure conditions with an absorption oil. The rich absorption oilcontaining the dissolved hydrocarbons is withdrawn from the bottom ofthe The process of my invention may be readily understood by referenceto the attached drawing illustrating modifications of the same. Forpurposes `of illustration, it is assumed that the feed gases comprisehydrocarbon constituents, having from one to seven carbon atoms in themolecule, and are derived from crude wfll separators. These gases areintroduced into. an initial compression zone I by means of feed line 2.These gases are compressed in zone I and are withdrawn IIJ-.means ofline '3. The hot compressed feed ga's stream withdrawn from zone I issegregated into a primary feed gas stream, which stream is passed toinitial cooling zone 4, and into a secondary feed gas stream whichstream is removed by means of line 2,2. The primary stream passed intoinitial cooling zone i is withdrawn by means of line 5, andintroducedinto initial separation zone 6. Condensed liquid is withdrawnfrom initial separation zone E by means of pump t and line 9. Thedesired liquidlevel is maintained in initial'separation zone 8 by meansof a oat control valve arrangement I0. Uncondensed vapors are removedoverhead from initial separation zone 6 by means of line I I, passed tosecondary compression zone I2, withdrawn `in any manner desirable.

yfrom said latter zone by meansy of line I3, cooled means of line I8,heated in heating zone i9 if desired, and combined with the liquidcondensate withdrawn from initial separation zone 0. The combinedcondensates are introduced i'nto stripping zone 2| in which theycountercurrently contact the segregated secondary feed stream of hotcompressed gases which is removed from initial compresion zone l andsegregated from said primary stream. These gases are introduced into thebottom section of stripping zone 2l by means of line 22. A liquidfraction substantially completely free of undesirable hydrocarbonconstituents is removed from the bottom of stripping zone 2I by means ofline 23, cooled in cooler 24 and withdrawn from the system by means ofline 25. This product is substantially free of undesirable relativelylow boiling constituents, is appreciably more stable than thecondensates removed from the initial and secondary separation zones andthus may be incorporated in motor fuels or preferably employed as anintermediate feed stockhfor alkylation, isomerization or other alliedprocesses. Uncondensed gases are withdrawn from stripping zone 2i bymeans of line 26 and mixed with the primary feed gas stream prior tocooling the same in initial cooling zone d. Under certain conditions itmay be desirable to withdraw at least a part of the condensate from theinitial separation zone from the system by means of line 2l.

The process of the present invention may be' widely varied. The processmay be adaptedv for the segregation ofany particular hydrocarbonfraction desirable constituents from any feed gas containing the same.The process, however, is particularly adapted for the segregation ofhydrocarbon constituents containing four or more carbon atomsfrom feedgases comprising hydrocarbon constituents containing one to seven carbonatoms in the molecule. The invention is especially adapted for theprocessing of gases of this character which are derived from crude oilwell separators. It is, however, to be understood that the invention maybe employed for treating feed gases derived from any refining,distilling, cracking, reforming or related operations. In general, it ispreferred that the feed gases be compressed in the initial separationzone to a pressure in the range of about 200-400 lbs. per square'inch,preferably to a pressure of about 260-320 lbs. per square inch. It isdesirable that the temperature of the gases be raised to a temperaturein the range from about 200 to 300 F., preferably to a temperature inthe range from about 225 to 275 F.

The relative proportions of the primary and secondary feed gas streamsmay vary considerably depending upon the character of the feed gasesandalso upon general operating conditions. In general it is desirablethat the secondary feed gas stream comprise at least 50% of the totalfeed gases. Particularly desirable results are secured when thesecondary feed gas stream comprises at least 75% of the total feedgas.

The extent to which the primary feed gas stream is cooled in the initialcooling zone will vary considerably and will depend to a large extentupon the character of the feed gases. However, it is preferred that theprimary gas stream be cooled in the initial cooling zone to atemperature below about 120 F., preferably to a temperature below about100 F. In general, it is desired to condense approximately 5% to 25% byvolume of the primary feed gas stream constituents.

The gases removed from the initial separation zone are compressed to arelatively high pressure in the general range from about 900 to about1800 pounds per square inch. Particularly desirable results aresecuredwhen these gases are compressed to a pressure in the range aboveabout 1500 pounds per square inch. The compressed gases are similarlycooled in the secondary cooling zone to a temperature below about 125F., preferably to a temperature in the range from about F. to 100 F.When operating without the stripping "zone, a condensate is produced'which contains a large percentage of hydrocarbons containing three orless carbon atoms in the molecule.

Although operating conditions in the stripping zone may be adjustedwithin relatively wide limits, it is preferred to maintain a pressure inthe stripping zone in the range from about 190 pounds to 390 pounds persquare inch and to maintain the temperature within said zone in therange from about 150 F. to 250 F'.

In order to illustrate the invention further, the following example isgiven which should not be construed as limiting the invention in anymanner whatsoeverz- Feed gases comprising hydrocarbon constituentscontaining from one to seven carbon atoms in the molecule werecompressed in an initial compression zone to about 265 pounds per squarel`inch. The temperature of the compressed gases was about 203 F. Thesegases were segregated into a primary feed gas stream comprising about25% of the total feed gases. This stream was cooled in an initialcooling zone to about F. whereby the pressure of the same was reduced toabout 230 pounds per square inch. The uncondensed vapors were separatedfrom the condensate in an initial separation zone and were compressedto' a pressure of about 940 pounds per square inch, whereby thetemperature of the same was increased Yto about 200 F. These gases werecooled in the secondary cooling zone to a temperature of about 90 F.,whereby the pressure of the gases wasL` reduced to aboutl 910 pounds persquare inch. The liquid condensates from the initial separation zone andfrom the secondary separation zone were combined and introduced into thetop of a stripping zone at a pressure of about 260 pounds per squareinch. These condensates countercurrently contacted the remainder of thefeed gases which had been segregated into a secondary feed gas stream insaid stripping zone. under conditions in which the temperature at thebottom of the stripping zone was maintained in the range from about F.to F.

` Liquid Feed gas Gas from v to primary secondary pggglet compresseparation stripper sion zone zone zone Mol Mol Mol 2. 4 1 5 z3. oI 3. 4 2. 2 32. 0 1. 6 0. 6 23. 0 l o. e o. 1 11.0

t l Volume -per cent.A 100 95. Ilv 4. 4

Nomar-0" with the sub-n`umeral represents the number of' the compressedgases Without cooling into a primary feed gas stream and into asecondary feed gas stream, cooling said primary feed gas stream in aninitial cooling zone, passing the mixture from said initial cooling zoneinto an initial separation zone wherein a separation is made betweenuncondensed vapors and the liquid condensate; passing said uncondensedvapors into a secondary compression zone, followed by cooling the samein a secondary cooling zone, passing the mixture from said. secondarycooling zone into a secondary separation zone wherein a separation ismade between uncondensed vapors and a liquid4 condensate, combiningrthecondensates from said initial separation zone and said secondaryseparation zone and countercurrently `contacting these condensates withsaid secondary feed gas stream in a stripping zone under conditions towithdraw as a liquid bottoms from said stripping zone a liquid productsubstantially free of undesirable hydrocarbon constituents.

2. Process as defined by claim 1, in which said compressed feed gaseswithdrawn from said initial compression zone are segregated into aprimary feed' gas stream comprising about 25% of the total volume offeed gases and into a secondary feed gas stream comprising about '75% ofthe total feed gases.

3. Process for the recovery and segregation of hydrocarbon constituentscontaining three or more carbon atoms in the molecule from feed gasescontaining the same, comprising hydrocarbon constituents containing fromone to seven carbon atoms in the molecule, which comprises compressingthe feed gases in an initial compression zone to a pressure in the rangefrom about 200 to about 400 pounds per square inch. segregating saidcompressed gases into a primary feed gas stream and into a secondaryfeed gas stream, cooling said primary feed gas stream to a temperaturebelow about 125 F., separatingr a liquid condensate fromuncondensedvapors vin an initial 'separation zone, compressing saiduncondensed vapors from said initial separation zone in a secondarycompression zone to a pressure in the range above 900 pounds per squareinch, cooling said compressed gases removed from said secondarycompression zone in a secondary cooling zone, and separating a. liquidcondensate from uncondensed vapors in a secondary separation zone,combining the condensates removed from the initial separation zone andthe secondary separation zone, and countercurrently contacting thecondensates with said secondary feed gas stream in a stripping zone at apressure of above about 190 pounds per square inch and at a temperatureabove about 150 F., whereby a bottoms stream is removed from saidstripping zone which is substantially free of hydrocarbon constituentscontaining less than two carbon atoms in the molecule.

4. Process as dened by claim 3, in which said compressed feed gaseswithdrawn from said initial compression zone aresegregated into a.primary feed gas stream comprising about 25% of the total volume of feedgases and into a secondary feed gas stream comprising about 75% of thetotal feed gases. Y

' WALTER H. RUPP.

